The invention relates to a process for regenerating electrolytes which contain sodium nitrate and are used for the electrochemical working of metallic workpieces within the pH range from 4 to 12, preferably from 6 to 9.
The electrochemical working of workpieces made of unalloyed or low-alloyed steel gives rise to coarsely flocculent metal hydrolysates, chiefly iron(III) hydroxide, which can easily be separated from the electrolyte by centrifuging or coagulating by means of flocculants.
In the case of other materials such as aluminium or alloyed steel, the metal hydrolysates, in particular of aluminium, iron, nickel and chromium, are largely obtained in very finely disperse form. Even by adding flocculating aids it is impossible to coagulate particles of adequate size which can be separated from the electrolyte by centrifugation, filtration or sedimentation.
It is an object of the present invention to separate out, by suitable measures, the very finely disperse metal hydrolysates produced in electrolytes which contain sodium nitrate in the working of metallic workpieces in such a coarsely flocculent form that they are readily filterable, sedimentable and centrifugable.